Design,synthesis and structure-activity relationship of 4,5-dihydropyrrolo[3,4-c]pyrazol-6(1H)-ones as potent p53-MDM2 inhibitors

In the past decade, the p53-MDM2 protein-protein interaction by small molecules has been confirmed as a successful strategy for cancer therapy. In our previous work, pyrrolo[3,4-c]pyrazol-6(1H)-ones were found to be potent p53-MDM2 inhibitors. Further optimization and structure-activity relationship studies were described in the present work. The result revealed that benzyl group on position N1 of imidazole and bromine on C4-phenyl of pyrrolidone showed higher inhibitory activities. In vitro antiproliferative assay demonstrated the potent p53-MDM2 inhibitor 5c with 4-fold selectivity for U2 OS and Saos-2 cells. These data indicated that 4,5-dihydropyrrolo[3,4-c]pyrazol-6(1H)-one moiety is a valuable scaffold for further development of p53-MDM2 inhibitors.     

Calcium sensing receptor forms complex with and is up-regulated by caveolin-1 in cultured human osteosarcoma (Saos-2) cells

The calcium sensing receptor (CaSR) plays an important role for sensing local changes in the extracellular calcium concentration ([Ca(2+)](o)) in bone remodeling. Although the function of CaSR is known, the regulatory mechanism of CaSR remains controversial. We report here the regulatory effect of caveolin on CaSR function as a process of CaSR regulation by using the human osteosarcoma cell line (Saos-2). The intracellular calcium concentration ([Ca(2+)](i)) was increased by an increment of [Ca(2+)](o). This [Ca(2+)](i) increment was inhibited by the pretreatment with NPS 2390, an antagonist of CaSR. RT-PCR and Western blot analysis of Saos-2 cells revealed the presence of CaSR, caveolin (Cav)-1 and -2 in both mRNA and protein expressions, but there was no expression of Cav-3 mRNA and protein in the cells. In the isolated caveolae-rich membrane fraction from Saos-2 cells, the CaSR, Cav-1 and Cav-2 proteins were localized in same fractions (fraction number 4 and 5). The immuno-precipitation experiment using the respective antibodies showed complex formation between the CaSR and Cav-1, but no complex formation of CaSR and Cav-2. Confocal microscopy also supported the co-localization of CaSR and Cav-1 at the plasma membrane. Functionally, the [Ca(2+)](o)-induced [Ca(2+)](i) increment was attenuated by the introduction of Cav-1 antisense oligodeoxynucleotide (ODN). From these results, in Saos-2 cells, the function of CaSR might be regulated by binding with Cav-1. Considering the decrement of CaSR activity by antisense ODN, Cav-1 up-regulates the function of CaSR under normal physiological conditions, and it may play an important role in the diverse pathophysiological processes of bone remodeling or in the CaSR-related disorders in the body.     

Triptolide sensitizes lung cancer cells to TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by inhibition of NF-kappaB activation

TNF-related apoptosis-inducing ligand (TRAIL/Apo- 2L), a newly identified member of the TNF family promotes apoptosis by binding to the transmembrane receptors (TRAIL-R1/DR4 and TRAIL-R2/DR5). TRAIL known to activate NF-kappaB in number of tumor cells including A549 (wt p53) and NCI-H1299 (null p53) lung cancer cells exerts relatively selective cytotoxic affects to the human tumor cell lines without much effect on the normal cells. We set out to identify an agent that would sensitize lung cancer cells to TRAIL-induced apoptosis through inhibition of NF-kappaB activation. We found that triptolide, an oxygenated diterpene extracted and purified from the Chinese herb Tripterygium wilfordii sensitized A549 and NCI-H1299 cells to TRAIL-induced apoptosis through inhibition of NF-kappaB activation. Pretreatment with MG132 which is a well-known NF-kappaB inhibitor by blocking degradation of IkappaBalpha also greatly sensitized lung cancer cells to TRAIL-induced apoptosis. Triptolide did not block DNA binding of NF-kappaB activated by TRAIL as in the case of TNF-alpha. It has been already proven that triptolide blocks transactivation of p65 which plays a key role in NF-kappaB activation. These observations suggest that triptolide may be a potentially useful drug to enhance TRAIL-induced tumor killing in lung cancer.     

Time-course expression of DNA repair-related genes in hepatocytes of zebrafish (Danio rerio) after UV-B exposure

The objective of this study was to evaluate the time-course effects of UV-B exposure on expression of genes involved in the DNA repair system of zebrafish ( Danio rerio ) hepatocytes, a highly competent species in terms of damage repair induced by UV radiation. For gene expression analysis (RT-PCR), cells were exposed to 23.3 mJ cm⁻² UV-B, which was the dose that affected viable cell number (reduction of 30% when compared with the control group) and produced no visual alteration on cell morphology. The early response observed (6 h) showed induction in the expression of the CDKI gene (cyclin-dependent kinase inhibitor) and genes related to DNA damage repair (mainly XPC and DDB2 ), while the late response observed (24 h) was more related to up-regulation of p53 and genes involved in cell cycle arrest ( gadd45a , cyclinG1 ). In all times analyzed, the anti-apoptotic gene Bcl-2 was down-regulated. Another interesting result observed was the up-regulation of the Apex- 1 gene after UV-B exposure, which could indicate the induction of oxidative lesions in the DNA molecule. In conclusion, these results demonstrate an activation of the DNA repair system in hepatocytes of zebrafish exposed to UV-B radiation, mainly involving the participation of p53.     

Low-dose radiation response of the p21WAF1/CIP1 gene promoter transduced by adeno-associated virus vector

In cancer gene therapy, restriction of antitumor transgene expression in a radiation field by use of ionizing radiation-inducible promoters is one of the promising approaches for tumor-specific gene delivery. Although tumor suppressor protein p53 is induced by low doses (< 1 Gy) of radiation, there have been only a few reports indicating potential utilization of a p53-target gene promoter, such as that of the p21 gene. This is mainly because the transiently transfected promoter of p53-target genes is not much sensitive to radiation. We examined the response of the p21 gene promoter to low-dose radiation when transduced into a human breast cancer cell line MCF-7 by use of recombinant adeno-associated virus (rAAV) vectors. It was shown that the p21 gene promoter transduced by rAAV vectors was more highly radiation-responsive than that transiently transfected by electroporation. A significant induction of the p21 gene promoter by radiation of low doses down to 0.2 Gy was observed. When cells were transduced with the p21 gene promoter-driven HSVtk gene by rAAV vector, they were significantly sensitized to repetitive treatment with low dose radiation (1 Gy) in the presence of the prodrug ganciclovir. It was therefore considered that the p21 gene promoter in combination with a rAAV vector is potentially usable for the development of a low-dose radiation-inducible vector for cancer gene therapy.     

Involvement of Heat-Shock Protein 70 and P53 Proteins in Attenuation of UVC-lnduced Apoptosis by Thermal Stress in Hepatocellular Carcinoma Cells

Induction of apoptosis is a function of external stimuli and cellular gene expression. Many cells respond to DNA damage by the induction of apoptosis, which depends on a functional p53 protein and is signaled by elevation of p53 levels. In this study, we found that a prior exposure to mild stress (42 degrees C) can protect HepG2 (p53+/+) cells from a subsequent UVC-induced apoptosis determined by DNA fragmentation and ratio of sub-G1 peak, but no heat-enhanced protection was found in Hep3B (p53-/-) cells. Although a similar inductive pattern of HSP70 protein and mRNA was detected in the two cell lines under thermal stress, the effect of thermal stress on UVC-induced apoptosis in HepG2 and Hep3B cells was obviously different. Overexpression of HSP70 by transient transfection of HSP70 expression vector in HepG2 cells significantly inhibited UVC-induced cell death; however, this inhibitory effect did not occur in transfected-Hep3B cells. Treatment of HepG2 cells with p53-specific antisense oligonucleotide could effectively block the antiapoptotic effect of thermal stress on UVC-induced apoptosis and increase of intracellular wild-type p53 protein by transfecting wtp53 expression plasmid into Hep3B cells yielded more resistance to UVC irradiation after prior thermal stress exposure. The results reveal an involvement of p53 in the antiapoptotic effect of thermal stress on UVC irradiation. Finally, a p53 protein increase was detected in UVC-treated HepG2 cells and could be coimmunoprecipitated with HSP70 after a thermal stress treatment. Prolonged p53 binding activity and enhanced expression of p53-controlled genes such as G1 arrest and DNA damage 45 and wild-type p53 activation factor 1/Cdk-interacting protein 1 by thermal stress are also observed in UVC-irradiated HepG2 cells. Based on these results, we propose that the antiapoptotic effect of thermal stress is mediated by increasing HSP70 and modulating intracellular p53 function.     

A new family of small molecules to probe the reactivation of mutant p53

Cells that express mutant p53 derived from cancers are selectively killed by a new class of small organic molecules. The protein p53 is recognized as one of the most important guardians in the body that prevents tumor development. Mutant forms of p53 are present in approximately 50% of all human cancers. Molecules that selectively kill cells expressing mutant p53 could become important chemotherapeutic agents. Our research focuses on developing a synthetically accessible class of molecules that can be easily modified to examine structural activity relationships and mechanism of biological activity or to optimize for anticancer activity. In this communication, a new class of molecules that selectively arrests growth of cells expressing two forms of mutant p53 is described. Synthetic routes to these compounds are also presented.     

Apoptosis-enhanced ferroptosis therapy of pancreatic carcinoma through PAMAM dendrimer-iron(III) complex-based plasmid delivery

The development of promising strategies to improve the treatment efficacy of pancreatic carcinoma still remains to be a challenging task. We report here the development of a new dendrimer-based nanomedicine formulation to tackle pancreatic carcinoma through apoptosis-enhanced ferroptosis therapy. In this article, G5 dendrimers were partially modified with a Fe(III) chelator hydroxyquinoline-2-carboxylic acid (8-HQC) on their periphery, entrapped with gold nanoparticles (Au NPs) within their internal cavities, and chelated with Fe(III). The thus created dendrimer-entrapped Au NPs (Fe-Au DENP-HQC) with an Au core size of 1.9 nm and 20.0 Fe(III) ions complexed per dendrimer are stable, have a pH-dependent Fe(III) release profile, and can generate reactive oxygen species under the tumor microenvironment (TME) and effectively compact plasmid DNA encoding p53 protein to form polyplexes with a hydrodynamic size of 143.9 nm and a surface potential of 33.6 mV. We show that cancer cells treated with the created Fe-Au DENP-HQC/p53 polyplexes can be more significantly inhibited through vector-mediated chemodynamic therapy (CDT) effect via Fe(III)-induced Fenton reaction and the p53 gene delivery-boosted cell apoptosis and oxidative stress in the TME than single-mode CDT and gene therapy. Further investigations using a xenografted tumor model validated the effectiveness of apoptosis-enhanced ferropotosis therapy through the downregulation of GPX-4 and SLC7A11 proteins, upregulation of p53 and PTEN proteins, as well as histological examinations. Meanwhile, the dendrimer nanoplatform enabled tumor fluorescence imaging through gene delivery-mediated enhanced green fluorescent protein expression. The Fe(III)-complexed dendrimer vector system may be developed as a promising theranostic nanoplatform for ferroptosis or ferroptosis-based combination therapy of other cancer types.

     

分子信标用于p53 mRNA的体外定量检测

根据p53基因的序列设计并合成了能特异性检测p53 mRNA的分子信标(MB), 发展了一种快速定量测定细胞内总RNA提取物中p53 mRNA的方法. 采用鼻咽癌(CNE2)细胞系和经RNA干扰技术降低p53基因表达的CNE2-p53RNAi细胞系, 抽提总RNA并用MB检测, 验证了MB的检测对象是p53 mRNA. 将该方法应用于多种肿瘤细胞内p53基因表达水平的分析, 表达变化趋势与经典的mRNA分析方法RT-PCR检测结果相符. 在此基础上, 用MB对5-氟尿嘧啶(5-Fu)处理的肺腺癌细胞(A549)进行了p53 mRNA的体外定量检测, 结果表明采用MB能够快速地获知该药物对细胞内p53 mRNA表达影响的信息.     

p53 overexpression represses androgen-mediated induction of NKX3.1 in a prostate cancer cell line

Prostate cancer is a disease involving complicated multiple-gene alterations. Both NKX3.1 and p53 are related to prostate cancer and play crucial roles in prostate cancer progression. However, little is known about the relationships and interactions between p53 and NKX3.1 in prostate cancer. We found that NKX3.1 expression is down-regulated by over-expression of wild type (wt) p53 in prostate cancer LNCaP cells. NKX3.1 is down-regulated at both the mRNA and protein levels by p53 over- expression due to either transient transfection of exogenous p53 or induction of endogenous p53. p53 over-expression represses androgen-induced transactivation of NKX3.1 by inhibiting the promoter of the androgen acceptor (AR) gene and by blocking AR-DNA binding activity. In addition, transfection with the p21 expression vector (pPSA-p21) showed that p21 does not reduce NKX3.1 expression, indicating that NKX3.1 expression is not the result of nonspecific effects of cell growth arrest. Our results provide biochemical and cellular biologic evidence that NKX3.1 is down-regulated by p53 over-expression in prostate cancer cells.     

Recombinant p53 displays heterogeneity during isoelectric focusing

Human recombinant, baculovirus‐expressed p53 protein focuses on 2D gels in multiple spots in the narrow pI range. Re‐electrophoresis of the individual spots resulted in the appearance of multiple spots. The strings of spots were neither species specific, nor characteristic for baculovirus‐expressed p53. Moreover, mutant p53 did not deviate from wild‐type p53, indicating that this is an inherent property of p53. Okadaic acid treatment of insect cells, phosphate substitution reaction of purified p53, and individual analysis of all spots by mass spectrometry revealed that only a fraction of the recombinant p53 is phosphorylated. This finding excluded that the individual p53 spots in 2D gels reflect charge isomers generated by phosphorylation, but rather suggest that they are due to conformational flexibility of urea‐denatured monomeric p53 molecules or deamidation of asparagine and glutamine residues. The latter possibility was confirmed by NanoLC‐ESI MS/MS analysis. Our data provide a putative hint for a novel regulatory level for function and stability of p53, particularly the long‐lived mutant p53 overexpressed in diverse tumor types.     

肿瘤抑制因子WT1对人的诱导型一氧化氮合成酶基因的转录调节作用

将人的诱导型一氧化氮合成酶(hiNOS)启动子构建在带荧光素酶基因的载体pGL3-basic上, 构建成用荧光素酶为系统的启动子, 以研究载体p8.3iNOS. 结果显示, 肾母细胞肿瘤抑制因子(WT1)能够有效地抑制hiNOS启动子的转录; 且WT1的4个选择性剪接本的抑制效果有所不同, 其中WT1(-/-)在两种肝癌细胞(HepG2和Hep3B)中对hiNOS的表达均具有最强的抑制作用, 并且抑制效果具有剂量依赖性, 用Western blot检测结果进一步证实HepG2细胞中WT1(-/-)过量表达能下调hiNOS表达. 以上结果说明WT1在肝癌细胞中对人的hiNOS具有转录调节作用.     

Ionizing radiation induces blockade of c-Jun N-terminal kinase-dependent cell death pathway in a manner correlated with p21(Cip/WAF1) induction in primary cultured normal human fibroblasts

During radiotherapy of cancer, neighboring normal cells may receive sub-lethal doses of radiation. To investigate whether such low levels of radiation modulate normal cell responses to death stimuli, primary cultured human fibroblasts were exposed to various doses of gamma-rays. Analysis of cell viability using an exclusion dye propidium iodide revealed that the irradiation up to 10 Gy killed the fibroblasts only to a minimal extent. In contrast, the cells efficiently lost their viability when exposed to 0.5-0.65 mM H(2)O(2). This type of cell death was accompanied by JNK activation, and was reversed by the use of a JNK-specific inhibitor SP600125. Interestingly, H(2)O(2) failed to kill the fibroblasts when these cells were pre-irradiated, 24 h before H(2)O(2) treatment, with 0.25-0.5 Gy of gamma-rays. These cytoprotective doses of gamma-rays did not enhance cellular capacity to degrade H(2)O(2), but elevated cellular levels of p21(Cip/WAF1), a p53 target that can suppress H(2)O(2)-induced cell death by blocking JNK activation. Consistently, H(2)O(2)-induced JNK activation was dramatically suppressed in the pre-irradiated cells. The overall data suggests that ionizing radiation can impart normal fibroblasts with a survival advantage against oxidative stress by blocking the process leading to JNK activation.     

β-Ketoiminato Iridium(III) Organometallic Complexes: Selective Cytotoxicity towards Colorectal Cancer Cells HCT116 p53-/-

This report presents a new library of organometallic iridium(III) compounds of the type [Cp*IrCl(L)] (Cp*=pentamethylcyclopentadienyl and L=a functionalized β-ketoiminato ligand) showing moderate to high cytotoxicity against a range of cancer cell lines. All compounds show increased activity towards colorectal cancer, with preferential activity observed against the immortalized p53-null colorectal cell line, HCT116 p53-/-, with sensitivity factors (SF) up to 26.7. Additionally, the compounds have excellent selectivity for cancerous cells when tested against normal cell types, with selectivity ratios (SR) up to 35.6, contrary to that of cisplatin, which is neither selective nor specific for cancerous cells (SF=0.43 and SR=0.7–2.3). This work provides a preliminary understanding of the cytotoxicity of iridium compounds in the absence of p53 and has potential applications in treatment of cancers for which the p53 gene is absent or mutant.     

The co-transfection of p16(INK4a) and p14(ARF) genes into human lung cancer cell line A549 and the effects on cell growth and chemosensitivity

Two functionally and structurally different proteins, p16(INK4a) and p14(ARF), encoded by the gene INK4a/ARF located at 9p21 are cyclin-dependent kinase (cdk) inhibitors and important cell cycle regulators. More and more evidences have been accumulated to show that the exogenous p16(INK4a) or p14(ARF) can inhibit the cell growth and/or induce the apoptosis. But it is still unclear if they can play positive role when combine with the conventional chemotherapy in cancer treatment. Here we show that cationic liposome-mediated gene transfection of INK4a/ARF into lung cancer cell line A549, in which the INK4a/ARF locus was lost, suppressed the growth and induced apoptosis. When treated with five different chemotherapy drugs with different mechanism after the transfection, A549 got an increased chemosensitivity for adriamycin and cisplatin and an unchanged result for topotecan, taxol or vinorelbine. The results indicated that cell cycle redistribution and increased apoptosis index after transfection might be the main explanation for the enhanced chemosensitivity. The combination of gene therapy with conventional chemotherapy is not always better than single chemotherapy. This trial will be of benefit to the treatment of lung cancer when combine the conventional chemotherapy and gene therapy in the future.     

MULTIPLE MODALITY TREATMENT OF CARCINOMA CELLS WITH Pt(Rh-123)2 PLUS X-RAY PLUS LIGHT

A complex of platinum tetrachloride with two molecules of rhodamine-123 (Rh-123), Pt(Rh-123)2, has been reported to act as hypoxic cell radiosensitizer of carcinoma cells in vitro and in vivo. In the present paper we report that Pt(Rh-123)2 photosensitizes human mammary carcinoma (MCF-7) cells and cis-platinum resistant human mammary carcinoma (MCF-7/CP) cells to 400-800 nm light in vitro. The efficiency of photosensitization by Pt(Rh-123)2 was 10 times greater than for Rh-123. Combination therapy using Pt(Rh-123)2 plus x-ray plus light was also much more effective compared to the combination therapy using Rh-123 plus x-ray plus light. After 15 microM of Rh-123 plus x-ray (0-8 Gy) plus light (5 J/cm2) treatment, cell survival curve was parallel to the x-ray cell survival curve with an initial decrease in the surviving fraction corresponding to the drug plus light mediated killing. Cell killing caused by Rh-123 (15 microM) plus x-ray (0-8 Gy) plus light (5 J/cm2) was additive as determined by the product of the surviving fraction after Rh-123 plus light and x-ray. In contrast, for 15 microM of Pt(Rh-123)2 plus x-ray (8 Gy) plus light (5 J/cm2) treatment, whereas additive killing predicts a survival fraction of approximately 0.024, in reality, the combination therapy caused the survival fraction to decrease to 0.0012, implying that the cell killing was enhanced by a factor of 20. Using Pt(Rh-123)2 plus x-ray plus light, supra-additive cell killing was also observed under hypoxic conditions, although compared to normally oxygenated conditions the degree of cytotoxicity was significantly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)     

Individually addressable submicron scale light-emitting devices based on electroluminescence of solid Ru(bpy)3(ClO4)2 films

A submicron light-emitting device (LED) was fabricated from lithographically fabricated parallel indium-tin oxide (ITO) finger electrodes (0.9 mum wide) separated by a 1.1 mum gap. A single layer of an amorphous (a) Ru(bpy)3(ClO4)2 film ( approximately 100 nm thick) was spin-coated on the electrode array. Ga:In or carbon paste was employed as a liftable upper contact electrode. Films ( approximately 1.5 mum thick) of single-crystal Ru(bpy)3(ClO4)2 (xyl) between two ITO electrodes in a sandwich cell were also prepared and produce electroluminescence. As with larger cells of this type, the high-resolution electroluminescence produced showed a high external efficiency ( approximately 3.4%), a low turn-on voltage (2.3 V), and reasonable stability. The single-crystal cells also behaved as photovoltaic devices and a short-circuit photocurrent was observed when they were irradiated without a bias voltage.     

Development of a packaging cell line for propagation of replication-deficient adenovirus vector

A human embryonic kidney cell line 293 is widely used for adenovirus production and propagation. With this cell line, however, replication-competent virus (RCV) is frequently generated, especially during large-scale production and successive propagation because 293 cells contain not only E1 gene but also non-E1 adenovirus gene. Homologous recombination between non-E1 region of 293 genomic DNA and its homologous region in the recombinant adenoviral vector generate RCV. To overcome this problem, we developed a new packaging cell line, Hela-E1, which contains minimum E1 region and from which non-E1 adenoviral region that is homologous with recombinant adenovirus vector was excluded. No RCV was detected during adenovirus propagation in Hela-E1 compared to in 293. In addition, adenovirus-p53 produced in HeLa-E1 was able to overexpress p53 protein when introduced into an ovarian cancer cell line, SKOV3. These results may have a significant impact on the development of packaging cell lines for replication-deficient adenovirus production.     

Heterologous expression of photoactivated adenylyl cyclase (PAC) genes from the flagellate Euglena gracilis in insect cells

The unicellular, green flagellate wild-type Euglena gracilis (strain Z) possesses two genes of the photoactivated adenylyl cyclase (PAC) family. The corresponding gene products were found to be responsible for step-up (but not step-down) photophobic responses as well as both positive and negative phototaxis. The proteins consist of two PACalpha (Mr 105 kDa) and two PACbeta (90 kDa) subunits. In an effort to produce sufficient amounts of PAC proteins, several routes of over-expression have been tried including homologous expression in Euglena and heterologous expression in Escherichia coli. All these approaches were hampered by low yield or formation of inclusion bodies. Therefore we decided to attempt a heterologous expression in an insect cell line. PACalpha and PACbeta were separately cloned in the transfer vector pBacPAK9 with a His tag attached. The transfer vector was subsequently cotransfected via baculovirus into the insect cells and amplified. For the expression both recombinant viruses (containing PACbeta and PACbeta, respectively) were cotransfected simultaneously into insect cells. The expressed proteins were analyzed in Western blots using PACalpha and PACbeta antibodies. Most of the proteins were found to be in soluble form in high yield. The recombinant PAC proteins were purified via their attached His tag on an anti-His resin. Adenylyl cyclase activity was quantified after blue-light excitation using a cAMP enzyme immunoassay kit.     

Semi-Synthesis of Small Molecules of Aminocarbazoles: Tumor Growth Inhibition and Potential Impact on p53

The tumor suppressor p53 is inactivated by mutation in approximately 50% of human cancers. Small molecules that bind and stabilize those mutants may represent effective anticancer drugs. Herein, we report the tumor cell growth inhibitory activity of carbazole alkaloids and amino derivatives, as well as their potential activation of p53. Twelve aminocarbazole alkaloids were semi-synthesized from heptaphylline (1), 7-methoxy heptaphylline (2), and 7-methoxymukonal (3), isolated from Clausena harmandiana, using a reductive amination protocol. Naturally-occurring carbazoles 1–3 and their amino derivatives were evaluated for their potential effect on wild-type and mutant p53 activity using a yeast screening assay and on human tumor cell lines. Naturally-occurring carbazoles 1–3 showed the most potent growth inhibitory effects on wild-type p53-expressing cells, being heptaphylline (1) the most promising in all the investigated cell lines. However, compound 1 also showed growth inhibition against non-tumor cells. Conversely, semi-synthetic aminocarbazole 1d showed an interesting growth inhibitory activity in tumor cells expressing both wild-type and mutant p53, exhibiting low growth inhibition on non-tumor cells. The yeast assay showed a potential reactivation of mutant p53 by heptaphylline derivatives, including compound 1d. The results obtained indicate that carbazole alkaloids may represent a promising starting point to search for new mutp53-reactivating agents with promising applications in cancer therapy.